permission denied after root droid x

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so the other day i rooted my phone by using the one button root and downloaded the wifi tether to check and make sure it works. everything worked fine. i also downloaded terminal emulator and checked to see if i can type in su. i did and that worked. a while back i read an article on how to edit the xml file on robo defense. says copy the xml file to sdcard which i was able to do then modify it and then stick it back in /data/data/com.magicwach.rdefense/shared_prefs. however everytime i try to copy it back it says permission denied using adb. so then i tried typing su in the command prompt after running adb shell. it then says permission denied. can anyone shine some light on this for me or what i may be doing wrong here? thanks in advance